1. WAVES: basics
Chapters ; 26

2. Simple Harmonic Motion
The equal or balanced back and forth or side to side motion of a particle that is caused to vibrate by a disturbance.
Similar to a pendulum’s motion.

3. WHAT IS A WAVE?
A repeating disturbance that causes vibrations and transmits energy through matter or space.

4. WHAT IS THE PURPOSE OF A WAVE?
To transmit energy from one place to another.

5. WHAT HAPPENS TO ENERGY AS THE WAVE TRAVELS?
Energy is transferred from one particle to the next.
The motion of particles in a medium is like the motion of masses on a spring.
Energy of the wave spreads away from the disturbance or vibration (see white board)

6. IS MATTER TRANSMITTED WITH THE WAVE?
No, only energy is transmitted.
The particles in the matter vibrate as the wave passes, but do not travel with the wave.

7. ARE THERE DIFFERENT TYPES OF WAVES?
Mechanical Waves
Non-Mechanical Waves
microwaves
Sound waves

8. Mechanical Waves Waves that can only travel through matter
Examples: sound, water and seismic waves
In general, mechanical waves travel fastest through solids, then slower through liquids and slowest through gases
Can be transverse or longitudinal (or compressional)

9. Non-Mechanical Waves
Waves that can travel through matter or space (a vacuum)
Example: electromagnetic radiation (waves) or light
In general, non-mechanical waves travel fastest through a vacuum, then slower through gases, then liquids and slowest through solids
Two perpendicular transverse waves

10. Electromagnetic Wave

11. Wave Speed
Wave speed (depends upon the composition and character of the medium it travels through)

12. Two types of waves based upon direction of vibrating particles:
Transverse Waves cause particles in matter to vibrate perpendicular to the direction of wave travel.
Longitudinal Waves cause particles in matter to vibrate in the same direction of wave travel.

13. TRANSVERSE WAVE
crest
One
wavelength
amplitude
Rest position
trough

14. LONGITUDINAL WAVE Rarefaction (less dense) Compression (more dense)
one wavelength

15. Wave Characteristics
Frequency (f) (the number of vibrations that occur in a given time)
Hertz (Hz) (# of vibrations per second)
High frequency waves produce waves with short periods and short wavelengths
Period (P) (the time it takes for one wave cycle to pass)
Seconds (s)
The lower the frequency, the longer the period

16. Wave Characteristics
Wavelength λ (lambda) (the distance between one point on a wave to the next identical point; crest to crest, for example)
Meters (m)
The lower the frequency, the longer the wavelength
Amplitude (longitudinal waves—the tightness of the compression; transverse waves—the distance from the crest to rest position or from trough to rest position)
The greater the amplitude of the wave, the more energy the wave transfers.

17. Frequency vs. Intensity
Rate of vibration (frequency)
Amount of energy (intensity)—
Amplitude (amount of displacement)
loudness (relative intensity of sound)
brightness (number of photons of light)
Turn up the volume--same frequencies, different intensity

18. Why do waves become less intense away from the source?
Same amount of energy is spread out over greater and greater distances.
Same energy at every point along a wave front.
Also, simple harmonic motion of the particles can be dampened (or absorbed or transferred) by the medium (rubber, clay, springs, fluids in shock absorbers)